Nonexhibition of Bragg phenomenon by chevronic sculptured thin films: Experiment and theory

Vikas Vepachedu, Patrick D. McAtee, Akhlesh Lakhtakia

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The unit cell of a chevronic sculptured thin film (ChevSTF) comprises two identical columnar thin films (CTFs) except that the nanocolumns of the first are oriented at an angle χ and nanocolumns of the second are oriented at an angle π-χ with respect to the interface of the two CTFs. A ChevSTF containing 10 unit cells was fabricated using resistive-heating physical vapor deposition of zinc selenide. Planewave reflectance and transmittance spectrums of this ChevSTF were measured for a wide variety of incidence conditions over the 500- to 900-nm range of the free-space wavelength. Despite its structural periodicity, the ChevSTF did not exhibit the Bragg phenomenon. Theoretical calculations with the CTFs modeled as biaxial dielectric materials indicated that the Bragg phenomenon would not be manifested for normal and near-normal incidence, but vestigial manifestation was possible for sufficiently oblique incidence. Thus, structural periodicity does not always lead to electromagnetic periodicity that underlies the exhibition of the Bragg phenomenon.

Original languageEnglish (US)
Article number036018
JournalJournal of Nanophotonics
Volume11
Issue number3
DOIs
StatePublished - Jul 1 2017

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Thin films
thin films
Experiments
periodic variations
incidence
zinc selenides
Physical vapor deposition
cells
transmittance
Zinc
vapor deposition
electromagnetism
reflectance
Heating
Wavelength
heating
wavelengths

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

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Nonexhibition of Bragg phenomenon by chevronic sculptured thin films : Experiment and theory. / Vepachedu, Vikas; McAtee, Patrick D.; Lakhtakia, Akhlesh.

In: Journal of Nanophotonics, Vol. 11, No. 3, 036018, 01.07.2017.

Research output: Contribution to journalArticle

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AU - Vepachedu, Vikas

AU - McAtee, Patrick D.

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AB - The unit cell of a chevronic sculptured thin film (ChevSTF) comprises two identical columnar thin films (CTFs) except that the nanocolumns of the first are oriented at an angle χ and nanocolumns of the second are oriented at an angle π-χ with respect to the interface of the two CTFs. A ChevSTF containing 10 unit cells was fabricated using resistive-heating physical vapor deposition of zinc selenide. Planewave reflectance and transmittance spectrums of this ChevSTF were measured for a wide variety of incidence conditions over the 500- to 900-nm range of the free-space wavelength. Despite its structural periodicity, the ChevSTF did not exhibit the Bragg phenomenon. Theoretical calculations with the CTFs modeled as biaxial dielectric materials indicated that the Bragg phenomenon would not be manifested for normal and near-normal incidence, but vestigial manifestation was possible for sufficiently oblique incidence. Thus, structural periodicity does not always lead to electromagnetic periodicity that underlies the exhibition of the Bragg phenomenon.

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